Roll-up shades are popular window coverings in which a flexible fabric or other material is suspended from a roller tube. In many instances, the roller tube is enclosed in a head rail that is mounted above the window to be covered. The roller tube can be rotated to raise and lower the shade. Thus, in conventional shades, the shade must be raised or lower to change the amount of light passing through the window, and the amount of light passing through the shade itself (per unit area) cannot be altered.
Because it is sometimes desirable to alter the amount of light per unit area passing through a window covering, i.e., to alter the opacity of a window covering in addition to raising and lowering the window covering, devices have been introduced which permit altering both the opacity of the window covering and which also permit raising and lowering the covering. Representative of these devices are horizontal mini-blinds, in which louvered slats of a blind can be moved between raised and lowered positions and also can be rotated in concert with each other between open and closed configurations. Rotating the slats alters the amount of light passing through the blind.
Similarly, Hunter-Douglas has introduced a roll-up shade device marketed under the name "Silhouette", in which horizontal strips of fabric are suspended between two sheets of fabric. The strips can be rotated only when the shade is in the fully lowered position to alter the opacity of the shade. Specifically, a mechanism can be operated to lower the shade completely, and then continued operation of the mechanism causes the strips to turn to the closed configuration. To open the strips, the mechanism is operated to raise the shade, which initially causes the strips to rotate to the open configuration. Continued operation of the mechanism raises the roll-up shade.
As recognized by the present invention, both mini-blinds and roll-up shades have certain drawbacks. With respect to mini-blinds, two mechanisms are necessary, one for raising/lowering the shade and one for opening/closing the slats. This increases the relative cost and complexity of mini-blinds. Moreover, the amount of light passing through the slats cannot easily be altered as the blind is being raised or lowered, because the slats can become fouled. Furthermore, the slats stack up against the bottom rail as they are raised, further complicating the ability to rotate the louvered slats between open and closed configurations when the blind is between the fully raised and fully lowered positions.
With respect to Silhouette.TM.-type roll-up shades, on the other hand, the strips cannot be rotated at all unless the shade is fully lowered. In shade positions above fully lowered, the amount of light passing through the shade per unit area simply cannot be altered. Thus, as a Silhouette.TM.-type roll-up shade is raised or lowered, and when the shade is in any position above the lowered position, the amount of light per unit area passing through the shade itself (i.e., its opacity) cannot be altered. Moreover, because the opacity of the Silhouette.TM.-type roll-up shade cannot be altered unless the shade is fully lowered, the length of the shade must be precisely measured to fit more or less exactly within the structure of the window sought to be covered, and if the length is even slightly longer or shorter than required for the particular window, the shade will not operate. Consequently, Silhouette.TM.-type roll-up shades are frequently mis-sized for the windows sought to be covered, and as a result have a relatively high return rate to the vendor.
As recognized by the present invention, however, it is desirable and possible that a window covering alter its opacity as the window covering is being raised or lowered, for pleasing, aesthetic effects. The present invention also recognizes that it is desirable and possible to facilitate altering the opacity of a shade-type window covering when the covering is in any position between fully raised and fully lowered, as might be desired by a user.
Accordingly, it is an object of the present invention to provide a window covering that alters its opacity when being raised and lowered. Another object of the present invention is to provide a shade-type window covering in which the opacity can be altered when the shade-type window covering is between the fully raised position and the fully lowered position. Still another object of the present invention is to provide a window covering which presents an aesthetically pleasing appearance when being raised or lowered. Yet another object of the present invention is to provide a window covering that is easy to use and cost effective to manufacture.